So I have a 98 f150 4x4 with the 4.6. My check engine light went off so I checked it, seems #8 had a misfire. Replaced spark plug. Nothing, so now I have replaced both coil packs the #8 injector, wires, sparks all the way around. The light stayed off for about 4 days came back on, now it flashes after leaving stop light, idles rough in gear. Still getting #8 misfire with the occasional #1 or #3. I'm completely lost now, anyone have any ideas?

 

Time to pull all 8 plugs and do a compression test on this motor. If #8 keeps coming back as a misfire, after plugs, wires and coil (set of 4), then you need to check if the cylinder is the culprit, and not the ignition system.

 

would the truck still run fine with a bad cylinder?

 

Either the engine is spent or you have Autolite Plugs in there. Autolite plugs in a nonPI engine is a bad mix. The cylinders will fail one by one.

 

It is NOT running Fine, if the engine has a misfire.

 

Lol, yea things will get MUCH worse if not taken care of. The cats will be the first to go. It does sound like bad plugs IMO. First #8, then #1 and 3. Classic Autolite drama. That happened to me too way back when. When others started experiencing the same thing with those plugs, I wrote Autolite and Honeywell and went back and forth with them. It was all posted online, then taken off later.

 

Who took it off?

 

I wasn't privy to that info, but if I had to guess, it to do with a marketer and IB. It took a year, but I was refunded for those plugs. I got an actual check in the mail lol.

 

So what brand of plugs should I run? Kinda scary but I got autolite double platinums in the truck. What's a non pi?

 

Non PI is the type of heads you have. Yea, the plugs are Ap/App 103's and 4's. It varied, my truck went 40 miles before the misfires began, I just barley made it home that night. Had to re-use my old plugs temporarily until I had time to purchase new.

The plugs to use are in your owners manual, Motorcraft. Motorcraft plugs are specified builds by Ford. Autolites are not and often can't handle the modular heat range. The two plugs are made side by side at the same plant. It's been said, the Autolite plugs come from the Motorcraft reject pile.